Composition comprising cement methyl siliconate salt and cellulose ether method of making and process of employing same



Feb. 9, 1960 F. J. SHELL ETAL 2,924,277

COMPOSITION COMPRISING CEMENT METHYL. sILIcoNATE SALT AND CELLULOSEETHER METHOD OF' MAKING AND PROCESS OF EMPLOYING SAME` 3 Sheets-Shee'r,vl

Filed. Marh 25. 1954 CEMENT AGENT IN V EN TORS. Hav/)cis I 676// /PagrSf/Y/ ATT #EVS Feb. 9, 1960 F, J, SHELL ETAL 2,924,277

4 COMPOSITION COMPRISING CEMENT METHYL SILICONATE SALT AND CELLULOSEETHER METHOD 0F MAKING AND PROCESS OF EMPLOYING SAME w Filed March 25.1954 s vsheets-sheet 2v Il e1 'F 5 u es n AT Feb. 9, 1960 F. J. SHELL.`ET AL4 2,924,277

COMPOSITION COMPRISING CEMENT METHYL SILICONATE SALT AND CELLULOSE ETHERMETHOD 0F MAKING AND PROCESS OF EMPLOYING SAME Filed March 25. 1954 I5Sheets-Sheet 3 ,o6 INVENToRs.

ATTOR/IEYS United States Patent() COMPOSITION COMPRISING CEMENT IVIETHYLSILICONATE SALT AND CELLULOSE ETHER METHOD OF MAKING AND PROCESS OF EM-PLOYING SAME Francis J. Shell, Bartlesville, Okla., and Robert D. Stili,Colfeyville, Kans., assignors to Phillips Petroleum Company, acorporation of Delaware Application March 2s, 1954, serial No. 418,7001o claims. (cl. 16s-as) This invention relates to cements havingretarded rates of hydration or set, to slurries of such cement, and tothe method of making these slurries. The cement with which the inventionis concerned is preferably a Portland or Portland-type cement. Inanother aspect it relates to any hydraulic cement composition in a dryform, or with added water in an aqueous slurry form, which when in theform of an aqueous slurry has a retarded initial set or extended orretarded thickening time and/or a reduced water-loss to adjacent porousformations, due to the addition of a minor but effective amount of aWater soluble salt of a methyl siliconate together with a selectedcellulose derivative, this invention relating first to said compositionsof matter, second to processes of compounding said compositions, andthird to processes for using said compositions in the arts of cementingwells, sealing porous formations during the drilling of wells, cementingcasings in the well, squeeze cementing, plugging the well or the earthformation adjacent the same, and grouting or sealing crevices, cracks orholes in manmade formations, such as buildings, foundations, dams,breakwaters or concrete and masonry structures, in some instances thecracks or fractures already existing before the slurry is pumped intothem, and in some cases the pressure of the slurry being pumped into oragainst the surface of said formation or structure forming by itspressure the cracks or fractures to be filled. In another aspect, thisinvention relates to a light weight cement incorporating diatomaceousearth as a weight-reducing agent together with selected cellulosederivatives and the aforesaid water soluble salt of a methyl siliconate.

Among the objects of the invention is the provision of a cement having aretarded rate of hydration, or retarded set, as it will be hereinaftertermed, particularly at elevated temperatures up to and above 300 F.and/or at high pressures up to and above 20,000 pounds per square inch,such as are encountered in cementing of deep Wells.

One object of the present invention is to provide a suitable hydrauliccement aqueous slurry, and suitable processes employing the same, forcementing casing in wells, for squeeze cementing in wells, and forgrouting cracks, fractures or voids, in natural formations, such as inwells, or in man-made formations such as dams, breakwaters, walls andmassive foundations and structures of all types.

Another object of this invention is to provide a dry hydraulic cementpowder which is a novel composition of matter, and which may be mixedwith water to formV an aqueous cement slurry which is a novelcomposition of matter and which has at least one of the following usefulproperties: a relatively retarded time of initial set, a relativelyextended thickening time during which it is pumpable, and/or arelatively low water-loss to porous formations with which it may, comein contact during cementing or grouting operations.

Further objects of the invention reside in the provision of a slurry ofthe above cement, and in a method of making such slurry. l v Y fr' 1C@These and further objects of the invention will be more readily apparentin the following description.

ln the cementing of oil wells it is customary to mix a hydraulic cement,for example a Portland or Portlandtype cement, withthe requisite amountof water to form a pumpable neat slurry, and to pump the mixture intothe well and down the hole into the place Where it is desired to have itharden. ln present oil well drilling practice, with Wells commonlyranging from 6,000 to 12,000 feet or more in depth, high temperaturesare encountered at the locations which are to be cemented, andrelatively long periods of time are often required to pump the slurryinto place. Furthermore, in the customary practice of pumping the cementslurry down through the casing and either forcing it out the bottom ofthe casing and upward around the outer surface of the casing, or throughperforations in the lower end of the casing into the formation sought tobe sealed, the slurry is required to pass through narrow channels andsmall openings. Successful placement of the slurry, therefore, requiresthat the slurry shall remain uid and pumpable at high temperatures forseveral hours before it begins to harden. However, after the slurry hasbeen pumped into place, it is desirable to have the hydration or setproceed at a rate at which the slurry will attain its nal set anddevelop considerable strength within a reasonable time, say within a fewdays. lt would be even more desirable to have it attain its nal set inabout 24 hours but often this is not attainable As pointed out in thepreceding paragraph, the most important function of the hydraulic cementaqueous slurry of the present invention is that it has a retarded timeof initial set, and therefore remains pumpable for a relatively longperiod of time and a relatively long period of time passes before itthickens, yet it will attain a final set of some considerable strengthwithin a reasonable length of time so that the well-drilling crew is notunduly delayed, but can get back to work and proceed to continuedrilling the well bore, or to perforate the casing and/or cement withthe usual gun perforating tools known to the art.- All types of theagents hereafter named, in suitable combination, have sufficient setretarding and thickening time extending properties when added tohydraulic cement aqueous slurries to be used commercially in thepractice of the present invention. A secondary eect is achieved, whichis also' of considerable value in cementing oil Wells, namely, the.aqueous cement slurry containing the minor but effective amount of oneof said named agents has a reduced tendency to lose Water to porousformations across the surface of which it must pass in going to itsintended position in the well. Many failures in prior art oil wellcementing jobs, which have been accredited to the premature setting ofthe cement, are thought to be caused actually by the formationdehydrating the cement slurry, thereby rendering the cement immobilebefore it reaches the desired position. As the practice of usingscrapers to clean the mud off the well walls to obtain a bettercement-formation bond becomes more frequently used, the better theformations will absorb the water from the cement slurry causing it notonly to plug the annulus between the casing and the .wall of the well,but also to have insufficient water for normal hydration upon setting,and the greater will become the realization of the need for lowwater-loss cements.

Everything which is said applying to natural formations in wells appliesalso in some degree to man-made formations being grouted, and the wordformation" as used herein is regarded as generic to natural earthformations, geological formations, and man-made formations t v such asstructures.

In the prior art of squeeze cementing in wells and in forcing "grout"into" the crcksand crevices 1n fractured foundations or the like, ithasl been the practice to employ to the formation or foundations@rapidly that the cement slurry would start to set beforemuchpenetration: has (been effected. When a relatively low water-losshydraulic cement aqueous slurry is employed, the amount of breakdow'nliquid can be greatly reduced, or entirely eliminated,because the lowwater-loss cement slurry will penetrate to muchgreater distances beforelosing suicient water to be caused to set by this` dehydration. Whensqueeze cementing in oil wellsjisfinvolved,A inwhich it isdesiredto'force a thin'disk or la'ye'rofthesel cement' slurries outinto`'a naturalA earth formationr along preexisting for pressure-madefractures, in ,order to'fseparate an oilsand-frorn` some other sand atthe'gen'eral vicinity where the oil wellinter's'ects the same, itvises'pecially advantageous to use a relatively low water-loss cementslurry a's breakdown agent because then less water is likely'to beabsorbed by theoil formation where it might cause a reduction in the`present or future amount of productionof oil.` Some oil-bearingformations contain bentonitic materials whichwswell when they encounterwater, and lif excess water is injected into such formations, theswelling ofthe bentonitic material may'prevent future production of oil.

In the drawings:

Figure 1 is an elevationalview with parts in section of apparatussuitable to carry out the processes of the present invention incompoundingthe hydraulic cement aqueous slurry' and cementing a-casingin a well, orgrouting a formation.`

FigureZ` is a crosssectonal view of a portion of a well in which squeezecementing is beingA employed to place a cementitious horizontal dam outinto the surrounding formation.

Figure 3 is a cross `sectionalview of a portion of a well in which a:porous formation is plugged to prevent loss of circulation while"drilling. i

Figure 1` illustrates-some of the processesdevised by the presentinvention for cementing a casing 4 in a well 6 drilled in formation7, orforgrouting cracks or crevices 1n formation 7,it being understood thatformation 7, instead offbeing-anatural geological formation, may be aman-madelformation such as a foundation, dam, breakwater, or otherconcrete or masonarylstructure. While casingf4` couldbe placed ini theopen bore 6 of the well, and the, circulated drilling mud, hydrauliccement aqueous slurry, orother fluids in the bore 6 could be allowed to`emerge around pipe4 onto the surface of the formation 7f from theuncased bore 6, it is preferred to have at least one casing, soilV pipe,or other pipe 8 secured in sealing contact with formation 7, ether'byclose lit or by previous cementing 9. The pipe 8 is provided with acasing head1-1 having a stuffing box or packing 12 forced into sealingcontact with casing 4 by somev sort of follower 13. Casing head 11 alsois provided with an outlet pipe 144` which-is preferably controlled byavalve 16V and which may discharge into a mud pit generally designated as17` through pipe 178. l t

A suitable amountv of a suitable grade `of hydraulic cement, such asPortland cement, is fed` from bin 19 throughl valve 21' into mixer 22and a minor but elective amount of one or more of saidnamed agents, sayfrom 0.3010 percent by weight of the dry hydraulic cement, for'example,0.5 percent by weight, is alsotfed into mixer 22 from` the `bin1 23controlled y'by valve. 24; Of course this, mixingyin` mixer 22 need notoccur anywhere near thewell,` but could have takenplace any number ofmiles away and several months before. and then ,the `ready- 4 i mixedcement composition brought to the well in sacks (not shown) or in a`bulk cement truck (not Shown); In any event the dry cement compositionfrom mixer 22, or from cement sacks'(not shown), is dumped into hopper26 wherepit is picked up andmixed with a jet of water` from tank 27controlled by valve 28, `or with a jet of drilling mudrZSbfrom mud pit17` through pipel 31 controlled by valvel32, the selected liquid beingforced `by Y pump 33, through -jet pipe-34. The jet of liquid from 34picks up and mixes with the dry cement from hopper 26 and discharges thesameout opening-36,` which4 could connect directly tocasing 4rr To,`insurethorough mixing, allow for inspection, and, act` as` a surgereservoir, a suit-` able reservoir 37 is generally provided and we havefound it useful to have a baille in the same, over which the hydrauliccement aqueousslurry owspancl is then picked up by pipe 41 controlled byvalve 42 from which 1t may t be pumped b y pump 43 into casing-4fthrough lpipe `44 valves 49 and`51, respectively, areboth reservedfordrilling mud29 from mud pit ,17, drawn `through pipe-52 controlled byvalve-S3 whendesired, or` water from tank 54` drawn through-pipe`56,controlledibyvalve.57 `when de-` While not essential, it is usefultollhave a pressure gauge toV y nular space 64 of Well bore 6 witheither drilling mud 29 59 connected atsorne,point'irrgtlie;system.`Thepressure gauge can be cut off byrvralvel." Y While casing `4couldbeiicemeuted `without the use of plugs 62and 63 simply byopeningvalves`16, 42, and` 49, andpumpingthehydraulic ycement aqueous slurry` withpump .43`down inside of casing 4,1outthe end thereof and up around theannular space1 64between bore 6 and casing 4;'on` tothe ground. surface66 aroundcasing 4 (if no soil pipe S is employed) this iwould notproduce the best type, of cementingayailable as the interior of thccasing 4 wouldl'be full` of cement'fwhichwould have to be drilled out,nandno pump pressure could` be placed on theA slurry. ,'Whethe'r soilpipe 8'is` present for pressure control tor not, Iit is possible,`wliendesiredinv the process, to` closev a1ve42` and. open ,eitheryalve153 or57 and follow the cement Wi'thwater S21-or `drilling"mud 29, and bycountirlgir 'the strokes of' the pump, aricly .stopping the same and`closing valve, 49A at the pfoper'rtime `to stop the cement waterintefacel before the, drilling, mud or water comesotlthfe'bottomof'casingI landfthus cement without plugsf62"and`,63aindlstill hal-vecsing almostfree of ce1 11eut. `V `By ,providingsoilpipe8, casirigl'iead,11,` flow line 184Valve71v6fan`d`casingfhead-SSQit is easytofplace` pressure'onr t'lie slurybythrottlingr `closing valve 16 whendesired; i

The two plug methodjillustfated, however, is preferred. Starting withplug "62, secured. incasing head S8Bbetween shown with set screws68"'and` all `.frvalves ,42, 53, 57, 51,46, 14S? and116 closed, Vit isusualto first wash the anor waterm54, 4in most cases drilling mud29`being preferred, and to do so ,valves`53 andV 57` are opened, de-

pending on whether` drillingmud`29` or Water is used,

valveH 16. isopened and valve 49 is opened and pump 43 is started,'pumping `the drillingmud (or water)` through` casing 4 uprthrough.annular space 64 andV out through pipev 18. lAtythe same timecasing 4maybemovedup and down! through stuffing box A11,1, packing 12` beingloosened'by loosening follower 13, andcasing 4 may, `if desired,havesecured thereto walL scraper elements generally designated;` as 70which may comprise. `annular rings 69isecure`cltolcasing 4, mounting*more or less radialwire bristles, rods or strips '71Lwhchzh scrapethedrilling mud cake loff thewallslof wellfbore 6in ,order` to provide agood blond v betweenthe formation 7,,the well, andcasing 4. Any numberof Scrapers `69 `may 4beprm'ided andthe movement of casing 4 may be`great enough so that the scraping of one set of Scrapers 69 willoverlap the scraping of the next adjacent set, and to allow thismovement a exible section of pipe 72 may be provided in the line 73 frompump 43.

When the washing of the well and cleaning of the wells is suliicientlyaccomplished, pump 43 is stopped, and whichever of valves 53 and 57 areopened is closed. The casing 4 at that time is spaced from the bottom ofthe hole 6 a distance less than the length of plug 62 plus a portion ofthe length of plug 63 but greater than the length of plug 62. Follower13 of stung box 11 is adjusted to seal at 12 around casing 4. Valves 16,42 and 46 are open and set screw 67 is screwed away, releasing plug 62,and pump 43 is started, pumping hydraulic cement aqueous slurry fromsump 74 of reservoir 37 into the space between plugs 62 and 63, forcingplug 62 down casing 4 and out the end thereof into the position shown.The cement forces the plug out the end of casing 4 and proceeds up theannulus 64 forcing the mud or water ahead of it up annulus 64 and indoing so it may have to traverse an especially porous formation-7 6which will take the water away from the aqueous slurry in the absence ofsaid named agent 23, especially if the drilling mud has been scrapedfrom the surface of formation 76 by the Scrapers 71. When the hydrauliccement aqueous slurry commences emerging from pipe 18, or when it isbelieved that it would emerge from pipe 18 or would reach the desiredelevation in annulus 64 as soon as casing 4 were cleared of cement,depending on the type of cementing job desired, then valve 51 and one ofvalves 53 or 57 are opened, set screw 68 is loosened, and valves 42 and46 are closed, whereupon the water (or drilling mud) passes through pipe48 into casing head 58, moving plug 63 down the casing 4 until plug 63rests on top of plug 62 but is unable to come out of the bottom of thecasing and therefore plugs the end of casing 4, whereupon the pressure(as indicated by gauge 59) goes up as an indication of what hashappened, valve 51 is closed and pump 43 shut down, leaving the annularspace 64 full of cement. and the inside of casing 4 full of water ordrilling mud.

Any time during the entire pumping process from the time the cementreaches 76 until plug 63 seats on plug 62 that it is desired to drivethe hydraulic cement acqueous slurry into the more porous portions ofthe formation, such as formation 76, it is only necessary to throttlepipe 18 by partially closing valve 16, or, if desired, to close valve 16completely for the desired time, which action will send up the pressurein the system to the desired degree and force cement slurry intoformation 76 if it will take the same at the pressure.

The U.S. patents now in class 166, Wells, subclass 22, Cementing orPlugging, disclose a number of other suitable cementing processes whichmay be employed in my invention.

Figure 2 is illustrative of a well 77 similar to well 6 and equippedwith similar equipment in which a squeezecementing job is employed toplace a cementitious horizontal dam 78 out into the surroundingformation 79.

As will be noted by the use of similar numbers, theV equipment at thetop of the well is all the same as in Figure 1 and is operated in thesame manner. Casing 4A dilfers from casing 4 somewhat, in that the`intermediate portion of casing 4A is provided with a number of radialholes 81 which holes are at first covered by sleeve 83 held in place byfrangible pin 82. When plug H 62 comes down the casing 4A ahead of thecement it catches in sleeve 83, breaks frangible pin 82 and opensopenings 81 to cement. rl`his causes a jump of the indicator needle ofgauge 59 and at that time valve 16 can be closed for as long a period oftime as desired so that cement 78 can be forced away out into formation79. When plug 63, which is followed by liquid 84 which may be water 54or drilling mud 29, reaches the top of plug 62 it plugs the interior ofcasing 4A, closing the holes 81. Incidentially, in both Figures l and 2,plugs 62 and 63 are preferably made of wood, or some easily drillableplastic composition, and preferably sleeve 83 is made of some drillablematerial, such as aluminum or magnesium, so that after cement dike 78has set, the casing 4A can be drilled out to its original diameter anddrilling or other desired operations carried out through the same.

In Figure 2 the formations 86 and 87 may be more impervious thanformation 79, and the crack into which cement 78 is forced may haveoriginally been formed by the pressure on the aqueous slurry of pump 43with valve 16 closed, in which case formation 86 and all overlyingformations are raised or compressed enough to make room for cement 78.These formations 86, 87 and 79 may all be man-made, such as layers ofearth, concrete or masonry, as in a big dam or other foundation.

InFigure 3 is illustrated rotary drilling operations in which a well 88is being drilled with a iishtail bit 89 rotated at the end of a drillstring 91. Drill vstring 91 has a square section 92 known as a Kellywhich is slideably and rotatably engaged with a square hole or bushingin rotary table 93, the drill bit being supported from eye 94 of rotaryswivel 96 by means of a hoisting tackle (not shown) and rotary `table 93is rotated through gear 97 driven by motor 98. At the same time pump 43is pumping drilling mud 29 (see Figure l) through pipe 73, ilexiblesection 72 and rotary swivel 96 down the inside of Kelly 92 and drillstring 91 and out of the jet hole of bit 89, returning through annularspace 101 through soil pipe 8, valve 16 and pipe 18 into mud pit 17.Soil pipe 8 is provided with a stuiing box 11A, which because the Kellyis square has to have a rotatable portion 13A slideably packing againstthe square sides of Kelly 92. Such equipment is well known in the art ofdrilling wells, as shown by U.S. patents in class 166, Wells, subclass15, Controllers; and class 255, Earth Boring, subclass 19A, Rotary,Blowout Preventers.

Motor 98 and rotary table 93 are supported by oor 102 of the usualrotary well drilling rig, the remainder of which drilling rig is notshown but is well known to those skilled in the art.

When rotary drilling, sometimes a cavernous formation 103 isencountered, containing passages 104 and 106, which may have anapparently unlimited capacity for taking up drilling mud in thedirection shown by the arrows. When such a formation is encountered,instead of directing ordinary drilling mud 29 in through pipe 52 andpumping the same down drill string 91 with pump 42, valve 53 is closed(see Figure l) vand valve 32 is opened, pump 33 is started, valve 28being closed, and drilling mud is jetted through 34 and mixed withhydraulic cement containing one of said named agents which is dischargedas a hydraulic cement aqueous mud containing slurry into 39 from whichit is picked up by pipe 41, valve 42 being open,` and valves 53 and 57closed, by pump 43 and pumped down drill string 91. At this time valve16 may be closed to increase the pressure forcing the slurry back intocaverns 104 and 106, but closing valve 16 may be unnecessary if caverns104 and 106 are already taking the drilling mud completely. Whenever theoperator, because of rising pressure or the returning of slurriesthrough pipe 18, decides that caverns 104 and 106 are shut off andcirculation has been restored, valve 42 is closed and valve 53 isopened, valve 16 now'being opened, and the rotary drilling continues inthe usual manner with drilling mud 39 from rnud pit 17 washing theremains of the cement containing mud out of bore 101 and pipe 18.Obviously the pump 33 is shut down as soon as slurry 29 is no longerneeded, and pipe 18 can be deected to another mud pit or dumping place(not shown) to avoid the cementitious mud returninglto mud pit 17, untilcement free mud returns, and then it-can be deected back to mud pit 17 YThese formations being drilledmay be man-made as ina dam, or may benatural formations encounteredtas intoil well drilling.

Byv hydraulic cement 4this invention intends tolinclude all mixtures oflime, silica,and alumina, or of lime and magnesia, silica and aluminaland iron oxide (magnesia for example mayreplace part ofthe lime, andiron oxide a. part of .the alumina), as aregcommonly known. ashydraulic; cements... Hydraulic cements includehydraulic limes, grappiercements, pozzolan cements, naturaltscements, calcium sulfate or,` gypsumcements (such asplaster of Paris) andPortland cements. Pozzolan cementsinclude slag cements made Y from slaked lime and granulated blastfurnace slag.; Because .offits` superior strength, Portland cement ispreferred among the .hydraulic cements, but astheart of cementsrecognizeshydraulic cementsatlenitesclassand'asresults of. value may beobtained with one ofsail` named agents with-any member of that class, itis desired to claim all hydraulic cements. In addition to the ordinaryconstruction grades of Portland cement or other hydraulic cements,modified hydraulic cements and Portland cements designated.ashighearly-strength. cement, heat-resistant cement, and slowsettingcement may be used in the present invention.

In accordance with the invention, a suitable cement for oil wellcementing and grouting operations can be prepared by addition to thecement of from 0.06. to 2.0. percent by weight of a water soluble` saltof a methylsiliconate in. combination with 0.2 to 10.0 percentof methylcellulose or Vcarboxy-methyl hydroxy-ethyl cellulose. However,outstanding advantages of the vinvention are obltained with light weightcement containing 1 to L6,0'percent of a suitable weight-reducing agent,such as diatomaceousearth, one particularly suitable diatomaceous earthbeing Celite. With such cements, containing diatomaceous earth, thecellulose derivatives methyl celulose and carboxy-methyl hydroxy-ethylcellulose giver outstanding results. If the carboxy-methyl hydroxy-ethylcellulose, i,s used,' the total, substitution should :be between 0.5 and1.75, preferably about 1.0 substituent group per cellulose unit. Thedegree of substitution of the hydroxyethyl groups can vary between 0.35and 1.35 substituent group per cellulose uni-t, preferably 0.7, and thedegree of substitution of the carboxy-methyl groups can vary between0.1,5 and `1.2, preferably 0.3. Therefore, in the preferred embodiment,the number of carboxy-methyl groups is generally equal to about half ofthe number of hydroxy-,ethyl groups of the cellulose molecule.

As stated, anyV water soluble salts ofthe methyl siliconate compoundsare suitable. The preferred salt isV the sodium salt, Le., sodium methylsiliconate, due to its lower cost and commercial availability. The otheralkali metal salts are very suitable however and include the potassiumsalts, and .materials Y such as lithium, rubidium, and caesium, or theammonium or` organic base salts of one of the methyl` siliconates whichare water soluble. Typical organic base salts `which can be used arethose derived from ammonia such as methylamine, dimethylamine andordinary ammonium bases; also pyridine,

iron,-copper,`lead,.` silver, mercury, nickel, and all` other salts`Whichl are 'solublet in` Awater l or hydrolyzed in a hydraulic`cement;aqueous,slurry are useful in this invention`vvhereL-,the'aqueous,hydrauliccement*slurry is :quite alkaline.

The amount. ofuwater` added-tto the cementof the l present-inventionistnot critical, `it being obvious that sufcient water should be addedto form a pumpable slurry, and` that-When the slurry becomes pumpablenoyfurther water need .be` added. One `advantage `of the slurry` of thepresent inventionv/hen one of said named agents is used isr thatit is alow water-loss slurry, and therefore it is not necessary to add muchexcess water over the amountmaking1 thevslurry pumpable` as a reserve`for expectedI losses, whichl excess water might tend to reduce the nalcompressive t strength of the cement; As previously noted,Wherethefcement.contansCelite asvl a` Weight-reducing agent togetherwith one of the specified cellulose derivatives land alwater-,solublemethyl siliconate, the resulting-cementslurryphas a light weighttogether with a low water loss. t Further, it is easyto` mix, and thethickening` time is not excessive.

In particular, it has been found heretofore that, when Celite `ordiatomaceous earth is added to cement, the amount of water lossreducingagent must be increased in order to hold` the water losswithinprescribedlimits. However, when carboxy-methyl hydroxy-ethyl celluloseis added to the cement in addition tothe Celite, the setting time of thecement is `far too great. Theiaddition of other accelerator` agents to.cut-down the lossof ,setting time has been found, in general,toldestroy or counteract the desirableetfects of the carboxy-methylhydroxy-ethyl cellulose in reducing the water loss. However-,g`unexpectedly, where the additional accelerating agentlis a water solublesalt of a methyl siliconate, the setting time is reduced withoutdestroying the beneficial elect of the water loss reducing agent.

When methyl cellulose, an accelerator, is used asta water losscontrolagentin a.Celite-containing,cement,

the water soluble `salt of a methyl siliconate `provides a l retardedsetting `time without destroying the effectiveness of the methylcellulose in preventing water loss. l

SPECIFIC EXAMPLES In the specific examples set forth inthe followingtable, the ingredients `were, mixed in the proportions` indicated andsubjected to thickening tests in a Halliburton thickening time tester at180 F. according to the procedure described in API code 32, section XI-I(9). The; time indicated is that at which the slurry was no longerpumpable. The cements werev also tested for water-loss according to theprocedure ,set forth API code 29 for drilling muds. This .test measuresthe milliliters of filtrate thatcanA be forcedthrlough a standard lterpaper by a lb`./in.2 gauge pressure differential, which has been foundto be a very good indication of what water would be lost from an aqueouscement slun'ylto an exposed porous sand formation in an oil well.

Table Wt. Per- Water Water Thickening Portland Cement cent; CellulosePer- Per- Per- Initial Loss Loss Time, WtJgal. Brand Sodium Derivativecent cent cent; Water after after Hours, and (Pounds)` Methyl CelteWater Loss 0.5 hr. 1 hr. Minutes Silioonate Dewe V0 54 515 0:48 15.0 Di;0.3 0 54 258 0:04 15.0 20 140 390 1:51 11.7 20 140 600 Short 11. 7 1. 520 140l 66 17 0:41 11. 7 y 1. 5 20 140 35 10:08 1t. 7 Garboxymethyl 1. 520 140 6 7 9 53:26 hydroxyethyl. l

morpholine and: the like. l Invaddition, the alkaline earth metal saltssuch as .barium,.calcium, strontiumandmaguesium,. andthe,heavy,metalsalts such as` theV aluminum,

prepared from a Water-soluble saltof a-methylsiliconate,

From the foregoing tableyit will-be evident that cement l ethylcellulose exhibit the desirable characteristics of low weight, low waterloss, and a desirable setting time, which is not true where the namedingredients are used individually or in other combinations.

While the invention has been described in connection with a present,preferred embodiment thereof, it is to be understood that thisdescription is illustrative only and is not intended to limit theinvention.

We claim:

l. A cement capable of forming a fluid slurry when mixed with watercomprising a hydraulic cement, 0.2 to l percent by weight based on saidcement of a carbohydrate derivative selected from the group consistingof corboxy-methyl hydroxy-ethyl cellulose and methyl ce1- lulose, and0.6 to 2.0 percent by weight based on said cement of a water solublesalt of a methyl siliconate.

2. A cement capable of forming a tiuid slurry when mixed with watercomprising a Portland cement, 0.2 to l0 percent by weight based on saidcement of a carbohydrate derivative selected from the group consistingof carboxy-methyl hydroxy-ethyl cellulose and methyl ce1- lulose, and0.6 to 2.0 percent by weight based on said cement of a water solublesalt of a methyl siliconate.

3. A light-weight cement capable of forming a fluid slurry when mixedwith water, comprising Portland cement, 0.2 to 10.0 percent of acarbohydrate derivative selected from the group consisting ofcarboxy-methyl hydroxy-ethyl cellulose and methyl cellulose, 1 to 60percent diatomaceous earth, and 0.06 to 2.0 percent of a water solublesalt of a methyl siliconate, where each said percent is defined aspercent by weight of said cement.

4. A cement in accordance with claim 3 in which said water soluble saltis sodium methyl siliconate.

5. A cement in accordance with claim 3 in which the alkali metalsiliconate is potassium methyl siliconate.

6. A method of cementing a casing in a well which comprises pumping downthrough the casing an aqueous hydraulic cement slurry containing 0.2 topercent by weight based on said hydraulic cement of a carbohydratederivative selected from the group consisting of carboxymethylhydroxy-ethyl cellulose and methyl cellulose, and 0.06 to 2.0 percent byweight based on said hydraulic cement of a water soluble salt of amethyl siliconate,

7. A method of cementing a casing in a well which comprises pumping downthrough the casing an aqueous hydraulic cement slurry incorporating 0.2to 10 percent by weight based on said hydraulic cement of a carbohydratederivative selected from the group consisting of carboxy-methylhydroxy-ethyl cellulose and methyl cellulose, 1 to 60 percent by weightbased on said hydraulic cement of diatomaceous earth, and 0.06 to 2.0percent by weight based on said hydraulic cement of an alkali metal Ymethyl siliconate.

8. The process of producing a hydraulic cement aqueous slurry having anextended time of set which comprises admixing with hydraulic cement from0.2 to 10 percent by weight of a carbohydrate derivative selected fromthe group consisting of carboxy-methyl hydroxyethyl cellulose and methylcellulose, 0.06 to 2.0 precent by weight of an alkali metal methylsiliconate, and 1 to percent by weight of diatomaceous earth, and mixingtherewith sufficient water to produce a fluid slurry.

9. The process of cementing a hole which extends into a formation whichcomprises admixing with hydraulic cement from 0.2 to 10 percent byweight based on said hydraulic cement of a carbohydrate derivativeselected from the group consisting of carboxy-methyl hydroxy-ethylcellulose and methyl cellulose, 1 to 60 percent by weight based on saidhydraulic cement of diatomaceous earth, and 0.06 to 2.0 percent byweight based on said hydraulic cement of an alkali metal siliconate,mixing therewith suiicient water to produce a fluid hydraulic cementaqueous slurry having an extended thickening time, and introducing saidslurry into said hole into contact with said formation.

10, The process of cementing a Well which extends into a formation whichcomprises admixing with hydraulic cement from 0.2 to l0 percent byweight based on said hydraulic cement of a carbohydrate derivativeselected from the group consisting of carboxy-methyl hydroxy-ethylcellulose and methyl cellulose, 1 to 60 percent by weight based on saidhydraulic cement of diatomaceous earth, and 0.06 to 2.0 percent byweight based on said hydraulic cement of an alkali metal methylsiliconate, mixing therewith suicient water to produce a uid hydrauliccement aqueous slurry having an extended thickening time, andintroducing said slurry into said hole into contact with said formation.

References Cited in the le of this patent UNTED STATES PATENTS 2,198,120Lerch et al. Apr. 23, 1940 2,360,518 Scripture Oct. 17, 1944 2,427,683Ludwig Sept. 23, 1947 2,491,487 Faulwetter Dec. 20, 1949 2,549,507Morgan et al. Apr. 17, 1951 2,654,674 Frankenho Oct. 6, 1953 2,813,085MacMullen et al Nov. 12, 1957 FOREIGN PATENTS 675,188 Great Britain July9, 1952 701,668 Great Britain Dec. 30, 1953

0.06 TO 2.0 PERCENT BY WEIGHT BASED ON SAID HYDRULIC CEMENT OF A WATERSOLUBLE SALT OF A METHYL SILICONATE.
 6. A METHOD OF CEMENTING A CASINGIN A WELL WHICH COMPRISES PUMPING DOWN THROUGH THE CASING AN AQUEOUSHYDRAULIC CEMENT SLURRY CONTAINING 0.2 TO 10 PERCENT BY WEIGHT BASED ONSAID HYDRAULIC CEMENT OF CARBOHYDRATE DERIVATIVE SELECTED FROM THE GROUPCONSISTING OF CARBOXYMETHYL HYDROXY-ETHYL CELLULOSE AND METHYLCELLULOSE, AND